1. Field of the Invention
The present invention relates to a control device for a stepping motor and an image forming device using a stepping motor. Further, the present invention relates to a sequence control device.
2. Description of the Related Art
In general, a stepping motor is used to control rotation of a photoconductive drum and a transfer belt in an image forming device such as an MFP, a copier, and a printer. The stepping motor is a motor which is driven by supplying a predetermined excitation pattern to a driver. The stepping motor can be rotationally controlled for a step angle corresponding to the supplied excitation pattern, and is used in a wide variety of fields. As the excitation pattern, there are patterns such as 1 phase excitation, 2 phase excitation, and 1-2 phase excitation.
A control device for the stepping motor includes a timer and a clock signal is generated based on a reference timing signal generated in the timer. The clock signal is used to prepare the excitation pattern. Therefore, a rotational speed can be controlled by optionally setting a cycle of the timing signal from the timer.
On the other hand, processing of output control of the timer, control of a motor or the like has conventionally been carried out by incorporating a controlling function in a CPU or by using an exclusive IC. For example, when control of the stepping motor is carried out by using the CPU, a variety of types of control are carried during a period between start and stop of drive of the motor. These types of control have been carried out by internal interruption of the CPU and building a program by utilizing DMA (Direct Memory Access).
However, the CPU also carries out control of parts other than the motor. Therefore, the more there are targets to be controlled, the more the processing such as interruption which lowers performance of the CPU. For this reason, the control by the CPU has an upper limit in program processing. In order to reduce this restriction, the processing of the CPU needs to be dispersed. In order to achieve this, the above situation is responded by a method such as a plurality of the CPUs are used. When a plurality of the CPUs are used, peripheral devices such as ROM and RAM are necessary for each of the CPUs, and also a communication means for reciprocally reporting a state between the CPUs needs to be included.
Jpn. Pat. Appln. Laid-Open Publication No. 2001-359292 describes a motor control device for controlling traveling of a movable body. This is an example where region information is generated based on positional information and speed information in the traveling of the movable body, and parameters for controlling a motor set for each region are read out from a memory circuit to control the motor. However, the region information needs to be generated for an entire section of the traveling of the movable object, and a circuit configuration is complicated.
In addition, Jpn. Pat. Appln. Laid-Open Publication No. 8-168295 discloses a control method of a stepping motor. In this example, a drive voltage of the stepping motor is changed depending on an operating state to ensure activation and stoppage of the stepping motor.
In addition, Jpn. Pat. Appln. Laid-Open Publication No. 2002-268471 discloses an ASIC incorporating a programmable sequencer and an image forming device. In this example, the ASIC for controlling a power source is included in a copier, a printer, etc. The ASIC controls a change to a power conservation mode and a return sequence from the power conservation mode.
In addition, Jpn. Pat. Appln. Laid-Open Publication No. 7-311607 describes a sequence control method suitable for manufacturing a semiconductor device. In this example, a CPU is provided both on a console side and on a processing device side. Under control of the CPU on the console side, a plurality of operational commands and executing timings of operation are stored in a storage means. The operational commands are read out for each of the executing timing and processing is executed on the processing device side.
Further, Jpn. Pat. Appln. Laid-Open Publication No. 11-202913 discloses a control device of a Programmable Machine Controller. This example is for controlling a target to be controlled in accordance with a sequence program, and for carrying out interruption processing based on a change in a state of the target to be controlled.
The present invention provides a control device for a stepping motor, an image forming device, and a sequence control device, the control device for a stepping motor capable of controlling with a high degree of freedom by classifying basic control such as a stepping motor into a plurality of parts and executing processing sequentially.